A consumer watchdog in the UK, Which?, has said that the rules, which aim to curb advertising foods assessed as high in fat, salt and sugar ("HFSS") to children, are not working.

Which? conducted a two-week analysis and found adverts for products such as Coca-Cola, which reportedly contains 13 teaspoons of sugar per 500 ml, and Kellogg’s Coco Pops, which is more than one-third sugar, were broadcast during programmes popular with children and were not caught by recent restrictions.

The OFCOM rules state that adverts for HFSS foods are not allowed to be shown in or around programmes of particular appeal to under-16s. If the proportion of those under 16 watching a programme is 20 percent higher than the general viewing population, then the programme is considered to be of particular appeal to under-16s.

Which? revealed through its report that none of the programmes with the five highest child audiences is covered by the restrictions imposed by OFCOM in January.

Therefore, while shows such as "The Simpsons" and "SpongeBob Square Pants" are caught by the rules, other shows such as "Beat The Star" and "Animals Do The Funniest Things" are not, despite being watched by thousands more children.

According to the two-week analysis conducted by Which?, "Animals Do The Funniest Things," a home video show where viewers send in amusing clips of their animals, was viewed by 370,600 children under 16, and included adverts for Cadbury’s Creme Egg Twisted, Maryland Chocolate Chip Cookies, Nachos and Kraft’s Dairylea Dunkers.

By contrast, "Shaggy and Scooby Doo get a clue" and "SpongeBob Square Pants", which are both caught by OFCOM’s restrictions, did not have adverts for HFSS foods.

Which? food campaigner Clare Corbett said, "The ad restrictions may look good on paper but the reality is that the programmes most popular with children are slipping through the net. If these rules are going to be effective, then they have to apply to the programmes that children watch in the greatest numbers."

Chief executive of the Advertising Association, Baroness Peta Buscombe, called the Which? report "sensationalist, unconstructive and missing the point." She added, "Their list includes programmes clearly not aimed at children and films screened after 10 p.m. There clearly has to be an element of parental responsibility on which programmes they allow their children to view."

A Department for Culture, Media and Sport spokesman said, "Although children still see some of these advertisements, the current OFCOM regulations mean that the viewing of these adverts by children is reduced by an estimated 50%, an impressive amount. We appreciate that there are calls for further restrictions on UK TV advertising but these should be considered once we have had a chance to assess the impact of current measures."

OFCOM is set to report on the success of its restrictions in December this year.